Buggy code:
public class VersionedExtension2 extends VersionedExtensionCommon { private static final PathElement NEW_ELEMENT = PathElement . pathElement ( "new-element" ) ; private static final PathElement RENAMED = PathElement . pathElement ( "renamed" , "element" ) ; private static final SubsystemInitialization TEST_SUBSYSTEM = new SubsystemInitialization ( SUBSYSTEM_NAME , true ) ; private static final RejectExpressionValuesTransformer rejectExpressions = new RejectExpressionValuesTransformer ( "int" , "string" ) ; void processTestSubsystem ( final SubsystemRegistration subsystem , final ManagementResourceRegistration registration ) { registration . registerOperationHandler ( "update" , new OperationStepHandler ( ) { @ Override public void execute ( final OperationContext context , final ModelNode operation ) throws OperationFailedException { final Resource resource = context . readResourceForUpdate ( EMPTY_ADDRESS ) ; final ModelNode model = resource . getModel ( ) ; model . get ( "test-attribute" ) . set ( "test" ) ; context . getResult ( ) . set ( model ) ; context . stepCompleted ( ) ; } } , DESCRIPTION_PROVIDER ) ; registration . registerSubModel ( createResourceDefinition ( VersionedExtension2 . NEW_ELEMENT ) ) ; registration . registerSubModel ( createResourceDefinition ( VersionedExtension2 . RENAMED ) ) ; registration . registerOperationHandler ( "test" , new OperationStepHandler ( ) { @ Override public void execute ( OperationContext context , ModelNode operation ) throws OperationFailedException { context . getResult ( ) . set ( true ) ; <START_BUG> context . completeStep ( ) ; <END_BUG> } } , DESCRIPTION_PROVIDER , false , PUBLIC , EnumSet . of ( READ_ONLY ) ) ; final TransformersSubRegistration transformers = subsystem . registerModelTransformers ( ModelVersion . create ( 1 , 0 , 0 ) , VersionedExtension2 . RESOURCE_TRANSFORMER ) ; transformers . registerOperationTransformer ( WRITE_ATTRIBUTE_OPERATION , VersionedExtension2 . rejectExpressions . getWriteAttributeTransformer ( ) ) ; transformers . registerOperationTransformer ( "update" , new VersionedExtension2 . UpdateTransformer ( ) ) ; transformers . registerOperationTransformer ( "test" , new OperationTransformer ( ) { @ Override public TransformedOperation transformOperation ( TransformationContext context , PathAddress address , ModelNode operation ) throws OperationFailedException { return new TransformedOperation ( operation , new OperationResultTransformer ( ) { @ Override public ModelNode transformResult ( ModelNode result ) { result . get ( RESULT ) . set ( false ) ; return result ; } } ) ; } } ) ; final TransformersSubRegistration newElement = transformers . registerSubResource ( VersionedExtension2 . NEW_ELEMENT ) ; newElement . discardOperations ( COMMON_OPERATIONS ) ; transformers . registerSubResource ( VersionedExtension2 . RENAMED , AliasOperationTransformer . replaceLastElement ( PathElement . pathElement ( "element" , "renamed" ) ) ) ; } @ Override public void initialize ( final ExtensionContext context ) { } @ Override public void initializeParsers ( ExtensionParsingContext context ) { } static ResourceTransformer RESOURCE_TRANSFORMER = new ResourceTransformer ( ) { @ Override public void transformResource ( ResourceTransformationContext context , PathAddress address , Resource resource ) throws OperationFailedException { } } ; static class UpdateTransformer implements OperationTransformer { @ Override public TransformedOperation transformOperation ( final TransformationContext context , final PathAddress address , final ModelNode operation ) { } } }

Fix:
context . stepCompleted ( ) ;